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Kiln of the Castle

23 April 2008

Birmingham headquartered Castle Cement has brought ‘kiln 4’, at its Padeswood works in north Wales, into operation with speed control from ABB industrial drives. The drives and control specialist has installed two, 300 kW drives in master-follower arrangement.

Here, both drives have an individual gear box which in turn drives a common girth gear that is attached to the kiln shell. This means that the speed of the drives change as the kiln feed increases or decreases.

Dave Jones, electrical engineer at Castle Cement, said: ‘This speed control is essential for the quality of the product.’

The £68 million kiln 4 installation increased production at the works from 500,000 to over 800,000 tonnes of cement per year.

A 2MW ABB industrial drive, used on the ID fan, is claimed to decrease energy consumption of the 65 metre long kiln. The ID fan, located near the preheater tower, draws gases through the kiln, precalciner and cyclones before emitting them through the exhaust stack

There are three fans involved in the kiln process and each one is controlled by an ABB industrial drive. Apart from the 2MW ID fan, there is an exhaust fan, rated at 750kW that takes gases to the atmosphere via the dust collecting bag filters and a cooler fan rated at 560kW which takes the cooler exhaust gases to atmosphere.

A further four fans, rated 110 kW, 160 kW, 200 kW and 250 kW push the air into the grate cooler to reduce the temperature of the hot clinker to a set point.

All these airflows have to be adjusted and controlled as atmospheric conditions, process conditions and ventilation needs greatly effect the flow requirements.

‘We have about 3.5MW of variable speed drives on fan applications and we would expect a 25 to 30 per cent saving over conventional technology. Low voltage AC drives are primarily used for load matching resulting in significant energy saving as well as for reduced maintenance benefits,’ Jones said.

‘Maintenance is considerably reduced because many of the drives have replaced DC drives and slip ring motors which required replacement carbon brushes costing over £7,500 per year in total.’

By installing the ABB industrial drives on the kiln, the ID fan and the other fans, Castle Cement hopes to improve its profitability through increased system availability, energy savings and reduced maintenance.

Jones said an added bonus was the location of ABB Drives Alliance partner and supplier of the drives, Central Electrical.

‘Its ability to respond with spare parts and technical advice along with access to their technical teams, training and trouble shooting is beneficial.’

Castle Cement claims to be a pioneer in alternative fuels and will use Cemfuel, processed from the residue of recycled waste solvents, and Profuel, which comprises paper and plastic wastes, at Padeswood. In the future, vehicle tyres will also be used as an alternative fuel.

The opening of the new kiln has resulted in the closure of three existing kilns at Padeswood and two wet kilns at the company’s Ribblesdale works in Lancashire. Castle said this will reduce its carbon dioxide emissions by 17.5 per cent per tonne of cement produced against 2004 performance. Acid rain gases at Padeswood are forecast to be reduced by 75 per cent. Since the new kiln came into operation, dioxin levels have been reduced while sulphur dioxide emissions are down by over 90 per cent and carbon dioxide by 20 per cent.

Managing director of Castle Cement, Mike Eberlin, said: ‘Kiln 4 will lead to major improvements in the local environment. It will also help reduce Wales’ dependence on landfill sites while using waste both for cleaner production and lower energy consumption.’

The new kiln ensures an increased supply in the marketplace of light-coloured cement. The light colour is especially attractive to precast concrete manufacturers as it can allow a brighter finished product and when used, less pigment may be necessary to arrive at a specified shade.